Frame Relay service is composed of three elements: the physical access circuit, the Frame, Relay port, and the virtual circuit. The physical access circuit is usually a T1 or fractional T1 and is provided by the local exchange carrier (LEC) between the customer premise and the nearest central office (CO). The Frame Relay port is the physical access into the Frame Relay network, a port on the Frame Relay switch itself.

The access circuit rate and the Frame Relay port rate must match to eliminate the possibility of discarded packets during periods of congestion. The virtual circuit is a logical connection between Frame Relay ports that can be provided by the LEC for intra-lata Frame Relay or by the inter-exchange carrier (IXC) for inter-lata Frame Relay. The most common virtual circuit is a permanent virtual circuit (PVC), which is associated with a committed information rate (CIR). The PVC is identified at each end by a separate data-link connection identifier (DLCI) in Data-link connection identifiers over an interexchange carrier Frame Relay network.

This hypothetical implementation shows the Dallas corporate office connected to three branch offices in a common star topology (or hub and spoke). Each office connects to a LEC CO over a fractional T1 circuit, which terminates onto a Frame Relay port at the CO, and on to a Frame Relay capable router at the customer premise. The port rates and the access circuit rates match. PVCs are provisioned within the Frame Relay network between Dallas and each branch office. The CIR of each PVC is sized so that it is half the respective port rate, which is a common implementation. Each branch office is guaranteed its respective CIR, but it is also allowed to burst up to the port rate without any guarantees.

The port rate at Dallas is not quite double the aggregate CIR, but it does not need to be, because the expectation is that not all three branch offices will burst up to the maximum at the same time. In an implementation like this, the service is probably negotiated through a single vendor. But it is likely that Dallas and Houston are serviced by the same LEC, and that the Frame Relay is intra-lata, even if the service was negotiated through an IXC, such as AT&T or Sprint. The service between Dallas and the other two branch offices, however, is most likely inter-lata.